Silencer of internal-combustion engines



Dec. 19, 1922; 1,435,506.

;.L. DURR.

SILENCEB OF INTERNAL COMBUSTION ENGINES. FILED JULY 2,1920.

Patented Dec. 19, 19 22.

. UNITED STATES PATENT OFFICE.

LUDWIG DTTRR, OF FRIEDRICHSKAFEN, GERMANY, ASSIGNOR TO THE FIRM: LUFT- SCHIFFBAU ZEPPELIN GESELLSCHAFT MIT BESCHRANKTER HAFTUNG, OF FRIED RICHSHAFEN, GERMANY.

Application filed July 2, 1920. Serial No. 393,755.

7 '0 all whom it may concern Be it known that I, LUDWIG Diiim, a citizen of the German Empire, residing at Friedrichshafen a./B., Germany, have invented certain new and useful Improvements in Silencers of Internal-Combustion Engines, of which the following is a specification. f

My invention refers to internal-combustion engines and more especially to the silencers thereof. It is a well-known fact that the exhaust gases blowing off into the exhaust pipe, still possess a' considerable pressure and high temperature. to improve the efficiency of the engine, endeavours are made to reduce the pressure and the temperature in the silencer as much as possible. This problem could only be solved very imperfectly hitherto, and this applies more particularly to the case of motors for air-craft, the reason being found in the fact'that cooling water is only avziilable in limited quantities and that cooling worth mentioning at .all can only be achieved with the aid of long pipe-lines which increase the pressure at expulsion in the cylinder in consequence of their resistance.

It is the object of the invention to create as high as possible a vacuum at the exit opening of the exhaust pipe by utllizlng the law about the reciprocal conversion of pressure into velocity known from the ejector water air pump, furthermore, to reduce the back-pressure by this means and to utilize the vacuum created for the purpose of sucking in fresh. air. Accordingly the object of the invention is a silencer for internal-combustion engines especially suit able for air-craft, the exhaust-pipe of which is surrounded, at least in the vicinity of its exhaust opening, by a jacket pipe in such a manner that the end opening of theexhaust pipe forms the smaller base and the end opening of the jacket pipe played upon by the exhaust gases, the larger base of a slender frustum of a cone. I

In the drawings attached to this specification and forming part thereof, illustrates three modifications of a silencer embodying my invention in a purely diagrammatical manner.

Fig. 1 is a cross-section of a four-cylinder engine and of the silencer belonging to it.

In order Fig. 2 is the same with a somewhat different arrangement of the silencer, and

Fig. 3 is also the same with another variation in the arrangement of the silencer.

I shall proceed to discuss according to Fig. 1 first.

The exhaust openings of four cylinders A, A A A are connected with an exhaust receiver tube D b means of a connecting piece (1.. The ex ust tube D ta ers slightly towards its exit opening J. ft is enclosed in a jacket tube E of sli and a suitable coolingmedium flows through the hollow space G thus created.

Assuming for the present that the jacket tube E does not exist and that there is a certain pressure p in the exhaust receiver the arrangement ghtly larger-diameter which projects a considertube B, then the exhaust. gases blow off directly into the open air through the opening d, i. e., they blow off with atmospheric pressure p and with a velocity 1; depending in the main on the pressure 12. Let us now imagine the exhaust pipe D lengthened beyond d and widening slightly conically (as indicated in Fig. 1- by the dot and dashlines) so that e becomes the exit opening. Then the exhaust gases completely fill the whole of the funnel-shaped space between the openings d and 6 without detaching themselves from the surface of" the funnel so long "as the opening'e does not go beond a certain multiple of the opening (1 ow the exhaust gases pass into the open atmosphere through the -opening, e and, with great approximation,-.aga1n possess the velocity ofwexit 1) provided that the pressure p in the exhaust receiver pipe B has not changed. In the opening d there fore a greater' velocity o is found .which has approximately the same proportion to *v as is the ratioof sectional ,area between opening e and openingd. Anlincreased ratio between the pressures in. the exhaust receiver pipe B andtheopening d respectively, however, corresponds to. the inally creased velocit Therefore, if the 4) -pressure p in the exhaust receiver pipe B remains unaltered, a considerable amount of vacuum must be the result at the openin (1. ln consequence or the increased sucking ofi of the exhaust gases there actuthe pressure in Y fVith the dropping of the pressure in the exhaust receiver pipe l3, however, the indicated work increases proportionately.

The above conditions remain very nearly unaltered, it the conical extension or the exhaustpipe D is left out and the jacket pipe E which is closed at its backward end 6 is added instead. The stream of exhaust gas issuing from d with great. velocity and a considerable vacuum, spreads out to a slender cone, a fact which can be observed without dificulty by employing a transparent jacket pipe, and at the moment of exit from the jacket-pipe E approximately possesses a sectional area equal to the area oijthe opening 6.

The vacuum prevailing in the the opening d of the jacket pipe is utilized for sucking in fresh cooling air either by leaving open the backward end 6 of the jacket pipe or by providing it with an entrance aperture offering resistance to the air flowing in. The fresh air flowing along the exhaust pipe D, cools the exhaust pipe and in the space between the openings (1' and e partly mixes with the still warmer exhaust gases, in this way contributing towards the extinction of sparks which might still be contained in the stream of exhaust gases. If there is no need to be intent in a particularly energetic cooling of the exhaust pipe D, the entrance openin 6 may also be connected with the space formed by the casing F, the air serving to cool the cylinders A, A A A and the exhaust receiver tube B being made to be sucked off by the exhaust gases blowing off at d, by this means. Fig. 2 illustrates a silencer pose. The entrance opening and the manner of guidance of the cooling air in the space G caused by the casing F, which do not form the object of the invention, are not detailed specially in the illustration.

A still thorough mixing of gases with the cooling air and consequently increase in cooling and power of suction can be achieved by designing the exhaust ipe D as a kind of ring-shaped tube (two concentric tubes) as will be perceived from the example illustrated in Fig. 3. This example of a possible manner of construction soon arises a state of inertia in which vicinity of:

the least possible arranged to serve this purthe exhaust menace difiers from the one illustrated in Fig. 1 in the followin points: The jacket pipe E which is exten ed conically in the vicinity of theexit opening 6 is deflectedat the opposite end to form a tube 153 arranged concentrically within the exhaust pipe D and possessing a smaller diameter than the latter and whose exit opening is situated in the same plane as that of the original exit opening d. Besides that, the jacket pipe E is joined to the cylinder-casing F by means of a connecting piece H arranged concentrically with the connecting piece C, but having a larger diameter.

' From the connecting piece C the exhaust gases therefore enter the ring-shaped hollow spacebetween the tubes D and E and through the ring-shaped nozzle J formed by the ends 01 these tubes, flow into the conical part of the jacket pipe E, where they storm a ring-shaped body deliminated by two cones. The velocity and the vacuum in the vicinity of the ring-shaped nozzle J are the same as in the example illustrated in Fig. 1, if the various component parts of the construction are selected and designed suitably. The great advantage of the arrangement 'lies in the fact that the cooling air can not only flow through the tube E so that the exhaust gases flowing out of the ring-shaped nozzle J are able to mix with cooler air in the central nucleus as well as the outer periphery, thereby being subjected to particularly energetic cooling. The suction efiect, though in a minor degree, is also increased. In thev case exemplified it is assumed that fresh air which. energetically cools the exhaust pipe, flows through the tube E and that the air coming from the engine, i. e., from the space G, flows through the ring-shaped space between the tubes D and E. However, the arrangement can of course easily also be modified in such a manner that the double previously already served to cool the cylinders A, A A A and the exhaust receiver pipe B.

I claim:

In a device of the kind described in combination, an exhaust pipe and a jacket, open at both'ends and connected with the cooling air space surrounding the cylinders, surroundlng the free end of said. pipe with a clearance and extending beyond it, the

diameter of the end'opening of said pipe being smaller than the diameter of the end opening of said jacket.

tug: testimony whereof I aflix my signa- LUDWIG DllR-R. 

